EP0178912B1 - A semiconductor laser - Google Patents

A semiconductor laser Download PDF

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Publication number
EP0178912B1
EP0178912B1 EP85307428A EP85307428A EP0178912B1 EP 0178912 B1 EP0178912 B1 EP 0178912B1 EP 85307428 A EP85307428 A EP 85307428A EP 85307428 A EP85307428 A EP 85307428A EP 0178912 B1 EP0178912 B1 EP 0178912B1
Authority
EP
European Patent Office
Prior art keywords
substrate
laser
operation area
striped
channel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP85307428A
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German (de)
English (en)
French (fr)
Other versions
EP0178912A2 (en
EP0178912A3 (en
Inventor
Nobuyuki Miyauchi
Shigeki Maei
Osamu Yamamoto
Taiji Morimoto
Hiroshi Hayashi
Saburo Yamamoto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sharp Corp
Original Assignee
Sharp Corp
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Publication date
Application filed by Sharp Corp filed Critical Sharp Corp
Publication of EP0178912A2 publication Critical patent/EP0178912A2/en
Publication of EP0178912A3 publication Critical patent/EP0178912A3/en
Application granted granted Critical
Publication of EP0178912B1 publication Critical patent/EP0178912B1/en
Expired legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/16—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
    • H01S5/24—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a grooved structure, e.g. V-grooved, crescent active layer in groove, VSIS laser

Definitions

  • This invention relates to a semiconductor laser with improved high output power operation characteristics. More particularly, it relates to a semiconductor laser which is excellent in reliability at a high power output of 30 mW or more per facet and which can attain laser oscillation in a stabilized fundamental transverse mode up to such a high output power.
  • the preamble of claim 1 corresponds to EP-A-0095826.
  • Window semiconductor lasers which can be operated for a long period of time at a high output power in which facet-breakdown usually occurs when output power is increased, and in which the absorption of laser light around the facets is reduced to suppress deterioration of the facets, were proposed, examples of which are a window-stripe laser reported by Applied Phys. Lett. 34(10), 15 May, 1979 p.637 and a crank type TJS laser reported by Jpn. J. Applied Phys. 21(1982) Supplement 21-1, p.347.
  • these window lasers do not have an optical waveguide in the direction parallel to the junction in the window region.
  • FIG. 7 shows the propagation of laser light within a conventional window semiconductor laser, wherein window regions 2 and 2', respectively, are formed from both ends 5 and 5' (from which the laser light is propagated with a wave-front 6) of a striped laser operation area 1 to the facets 3 and 3' (from which laser beams are emitted).
  • Beam waists are positioned at the end portions 5 and 5' of the laser operation area 1 in the direction parallel to the junction, while they are positioned at the facets 3 and 3' in the direction vertical to the junction, resulting in an astigmatism.
  • This astigmatism makes it difficult to concentrate light refracted by lenses, etc., in order to achieve optical coupling.
  • Japanese Patent Application No. 57-91636 which patent application is claimed as a priority document for the above-mentioned EP-A- 0 095 826, concerning a window semiconductor laser in which an optical waveguide is formed in the window region.
  • this window laser is that the portion of the active layer in the vicinity of the facets is a plane shape and the portion of the active layer inside of the facets is a crescent shape, said crescent portion being formed into a buried heterostructure, and accordingly window regions are formed in the vicinity of the facets and a stabilized fundamental transverse mode can be attained up to a high output power. Due to the buried heterostructure of the crescent portion of the active layer, current which does not contribute to laser oscillation can be reduced so that laser oscillation in a high-order transverse mode can be suppressed.
  • a window VSIS semiconductor laser having a laser operation area and window regions having end facets, comprising a substrate, a current blocking layer formed on said substrate; a striped channel formed in said current blocking layer on said substrate; said striped channel being narrower in the window regions and being wide within the laser operation area; a current injection region provided in the striped channel; a first cladding layer formed on said current blocking layer, a portion of the active layer corresponding to the window regions being planar and the portion of the active layer corresponding to the laser operation area having a crescent-shaped concavity.
  • the current injection region in one preferred embodiment, further comprises a striped V-shaped channel of the substrate, which is exposed along the center line of the narrow portion of said striped channel of the current blocking layer.
  • the current injection region is, in another preferred embodiment, composed of a striped mesa-portion of the substrate, which is exposed along the center line of both the wide and narrow portions of said striped channel of the current blocking layer.
  • the invention described herein makes possible the objects of: (1) providing a semiconductor laser in which the efficiency of contribution of the injection current to the laser oscillation operation is so high that stabilized laser oscillation can be attained at a high output power for a long period, and the threshold current level and the operation current level can be reduced; (2) providing a semiconductor laser in which the double-heterostructure within the laser operation area is surrounded by burying layers, so that current which does not contribute to laser oscillation can be blocked by the burying layers (i.e.
  • the inventor found by experimentation that in the case where a VSIS (V-channeled substrate inner stripe) laser with a crescent-shaped concavity in the active layer and a VSIS laser with a plane active layer are separately manufactured under the same crystal growth conditions, the former laser attains laser oscillation at a longer wavelength than the latter laser by from 10 to 20 nm, that is, the band-gap of the crescent active layer is narrower than that of the plane active layer by from 21 to 42 meV. Moreover, the curvature of the active layer makes the transverse mode less stable although the oscillation threshold current level becomes low, while the plane of the active layer makes the transverse mode stable, to a great extent, although the oscillation threshold current level becomes high.
  • VSIS V-channeled substrate inner stripe
  • Figure 1 shows the propagation of laser light in a semiconductor laser of this invention, in which window regions 22 and 22' having a waveguide width Wg2 and lengths Lw and L'w are connected to both ends 25 and 25' of a laser oscillation operation area (i.e., excitation area) 21 , and laser beams 24 and 24' are irradiated from the facets 23 and 23' , respectively.
  • Laser light is propagated in the window regions with the wave-front 26 .
  • FIGS 2(A) and 2(B) are sectional views showing the laser oscillation operation area 21 inside of the facets and the window region 22 (or 22' ) near the facets of the semiconductor laser shown in Figure 1 .
  • This semiconductor laser comprises a p-GaAs substrate 31 and an n-GaAs current blocking layer 32 formed on the substrate 31 .
  • the n-GaAs current blocking layer 32 has a striped channel which is composed of a Wc1 portion 320 and a Wc2 portion 321 which correspond to the laser oscillation operation area 21 and the window regions 22 and 22' , respectively.
  • This semiconductor laser further comprises, in the window regions as shown in Figure 2(B) , a double heterostructure for laser operation composed of a p-cladding layer 33 , an active layer 34 , an n-cladding layer 35 and an n-cap layer 37 .
  • a double heterostructure for laser operation composed of a p-cladding layer 33 , an active layer 34 , an n-cladding layer 35 and an n-cap layer 37 .
  • it further comprises an excitation area 30 having a mesa-structure composed of the p-cladding layer 33 , the active layer 34 , the n-cladding layer 35 and the n-cap layer 37 , which are successively formed on a mesa-portion 310 of the substrate 31 .
  • the excitation area 30 having a mesa-structure is then surrounded by burying layers 36 .
  • the width of the Wc1 channel portion 320 is greater than the width of the Wc2 channel portion 321 .
  • the portion of the active layer 34 grown above the channel portion 320 with the width Wc1 results in a downward curvature functioning as an excitation area for laser oscillation, while the portion of the active layer 34 grown above the channel portion 321 with the width Wc2 results in a plane shape functioning as a window region.
  • the mesa-portion 310 is positioned in the center of the channel pattern with the width Wc1, but it is not placed under the channel pattern with the width Wc2. Based on the channel pattern, the current blocking layer 32 is subjected to an etching treatment with an etching solution containing sulfuric acid.
  • Figures 4(C) and 4(D) show sectional views of the resulting striped channel which is composed of a Wc1 portion 320 (the X-X line in Figure 1) and a Wc2 portion 322 (the y-y line in Figure 1 ).
  • the mesa-portion 310 of the substrate 31 is exposed along the center line of the channel portion 320 having the width of Wc1.
  • the V-shaped channel portion 322 having the width of Wc2 reaches the substrate 31 through the current blocking layer 32 .
  • a p-Ga 0.5 Al 0.5 As cladding layer 33 , a p-Ga 0.85 Al 0.15 As active layer 34 and an n-Ga 0.5 Al 0.5 As cladding layer 35 are successively grown with thicknesses of 0.15 ⁇ m, 0.05 ⁇ m and 1 ⁇ m, respectively, in the plane portion of each thereof.
  • an n-cap layer 37 is formed on the n-cladding layer 35 to achieve ohmic contact with an electrode thereon.
  • the excitation area in the center portion shown in Figure 5 is mesa-etched with an etching solution containing sulfuric acid to eliminate the portion ranging from the top face of the grown layers to the surface of the current blocking layer 32 , resulting in the remaining portion of the grown layers which acts as a mesa for laser operation which is in contact with the mesa-portion 310 of the substrate 31 .
  • the width Wb of the mesa-portion 30 of the laser operation area is slightly greater than the width Wi of the mesa-portion 310 of the substrate 31 .
  • p-Ga 0.5 Al 0.5 As burying layers 36 having a high electrical resistance are grown by liquid phase epitaxy to surround the mesa-portion 30 , followed by subjecting the back of the substrate 31 to a wrapping treatment with a proper material to result in the substrate 31 with a thickness of approximately 100 ⁇ m. Then, the surface 38 of the grown layers and the back of the substrate 31 are subjected to a vacuum evaporation treatment with metal materials of Au-Ge-Ni and Au-Zn, respectively, followed by heating at 450°C to form electrode layers made of an alloy of Au-Ge-Ni and an alloy of Au-Zn, respectively. Then, Al is vacuum-evaporated on the back of the p-GaAs substrate 31 .
  • the resulting window semiconductor laser attained laser oscillation in a stabilised fundamental transverse mode at a wavelength of 780 nm at a threshold current of 15 mA up to the maximum output power, Pmax for the facet-breakdown, of 100 mW.
  • Pmax the maximum output power
  • Another window semiconductor laser which has an oscillation wavelength of 830 nm exhibited a Pmax of 200 mW when the facets were not coated with an Al2O3 film, and exhibited a Pmax of 400 mW when the facets were coated with an Al2O3 film.
  • the double heterostructure 30 for laser operation is constituted by a mesa-structure, the width Wb of which is the sage as or greater than the width Wi1 of the mesa-portion 310 of the substrate 31 within the channel portion 320 and which is in contact with the mesa-portion 310 , and moreover the burying layers 36 surrounding the mesa-structure 30 are in contact with the electroconductive region in the channel, current applied to the mesa-portion 310 can be infected into the excitation area of the active layer 34 without leakage.
  • the efficiency of the contribution of the injected current to laser oscillation becomes extremely high thereby enabling a high output power operation at a low threshold current level and at a low injection current level.
  • window lasers having wavelengths of 780 nm and 830 nm, respectively, could attain continuous operation without deterioration at an output power ranging from 40 to 50 mW at 50 °C for a long period.
  • Figure 3 shows the sectional view of another semiconductor laser of this invention at the portion corresponding to the Y-Y line in Figure 1 .
  • the sectional view thereof at the portion corresponding to the X-X line in Figure 1 is the same as that in Figure 2(A) showing the semiconductor laser in Example 1 .
  • the semiconductor laser in this Example comprises a substrate 31 having the striped mesa-portion 310 over the whole area (which corresponds to the laser operation area 21 and the window regions 22 and 22') of the resonator, although the semiconductor laser in Example 1 comprises the substrate 31 having the mesa-portion 310 in the portion corresponding to the laser operation area alone (i.e., the center portion of the resonator) 21 .
  • the width of the current injection region of the laser is, as the whole, the width Wi1 of the mesa-portion 310 of the substrate 31 .
  • a striped channel pattern is then formed on the surface of the current blocking layer 32 by photolithography in such a manner that, as shown in Figure 4(B) , the width Wc1 of the channel pattern inside of the facets is greater than the width Wc2 of the channel pattern in the vicinity of the facets.
  • Each portion of the channel pattern is the same shape and size as that of the channel pattern in Example 1 .
  • the current blocking layer 32 is subjected to an etching treatment with an etching solution containing sulfuric acid, resulting in a striped channel composed of a Wc1 portion 320 and a Wc2 portion 321 as shown in Figures 6(B) and 6(C) , respectively.
  • the mesa-portion 310 of the substrate is exposed along the center line of both the channel portion 320 (corresponding to the laser oscillation operation area 21 ) and the channel portion 321 (corresponding to the window regions 22 and 22' ). Then, the double heterostructure is successively formed by an epitaxial growth technique in the same manner as described in Example 1 , resulting in the desired window semiconductor laser.
  • This window semiconductor laser exhibited the same laser oscillation operation characteristics as obtained in Example 1 .
EP85307428A 1984-10-16 1985-10-15 A semiconductor laser Expired EP0178912B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP217782/84 1984-10-16
JP59217782A JPS6195593A (ja) 1984-10-16 1984-10-16 半導体レ−ザ素子

Publications (3)

Publication Number Publication Date
EP0178912A2 EP0178912A2 (en) 1986-04-23
EP0178912A3 EP0178912A3 (en) 1987-09-09
EP0178912B1 true EP0178912B1 (en) 1991-06-12

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EP85307428A Expired EP0178912B1 (en) 1984-10-16 1985-10-15 A semiconductor laser

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US (1) US4730328A (ja)
EP (1) EP0178912B1 (ja)
JP (1) JPS6195593A (ja)
DE (1) DE3583202D1 (ja)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6218783A (ja) * 1985-07-17 1987-01-27 Sharp Corp 半導体レ−ザ素子
JPH0671121B2 (ja) * 1987-09-04 1994-09-07 シャープ株式会社 半導体レーザ装置
GB2283858A (en) * 1993-11-12 1995-05-17 British Tech Group Semiconductor laser
US6996150B1 (en) 1994-09-14 2006-02-07 Rohm Co., Ltd. Semiconductor light emitting device and manufacturing method therefor
US7177330B2 (en) * 2003-03-17 2007-02-13 Hong Kong Polytechnic University Method and apparatus for controlling the polarization of an optical signal
JP4077348B2 (ja) * 2003-03-17 2008-04-16 松下電器産業株式会社 半導体レーザ装置およびそれを用いた光ピックアップ装置
DE102012110836A1 (de) * 2012-11-12 2014-02-27 Osram Opto Semiconductors Gmbh Optoelektronischer Halbleiterchip und Verfahren zur Herstellung von optoelektronischen Halbleiterchips

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS577183A (en) * 1980-06-16 1982-01-14 Nec Corp Fundamental transverse mode semiconductor laser and manufacture therefor
EP0095826B1 (en) * 1982-05-28 1988-06-01 Sharp Kabushiki Kaisha Semiconductor laser
JPS5940592A (ja) * 1982-08-30 1984-03-06 Sharp Corp 半導体レ−ザ素子

Also Published As

Publication number Publication date
JPH0114717B2 (ja) 1989-03-14
DE3583202D1 (de) 1991-07-18
US4730328A (en) 1988-03-08
EP0178912A2 (en) 1986-04-23
JPS6195593A (ja) 1986-05-14
EP0178912A3 (en) 1987-09-09

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